Portable headlamp

ABSTRACT

A portable headlamp that is particularly designed for use with bicycles integrates a number of essential features and functions desired by modem bicyclists. The headlamp has an easily removable and universally mountable fastening system that requires no tools to install. The mounting system includes a rotary joint that enables a headlamp to be pointed in any desired direction while maintaining a constant friction that can be set by the user. A focussable light beam enables the operator to vary the light distribution pattern, thereby making the headlamp suitable for use under a number of different conditions. The electrical system for the headlamp can be readily upgraded to accommodate the needs of different riding conditions, without requiring additional parts. All of these features are contained within a compact, streamlined housing that is designed to accommodate batteries in a manner that maintains the center of gravity of the headlamp coincident with its mounting point, thereby increasing its stability under rough riding conditions.

This application is a divisional of application Ser. No. 07/929,219, nowU.S. Pat. No. 5,436,810 filed Aug. 13, 1992.

FIELD OF THE INVENTION

The present invention is directed to a compact, portable light sourcethat can be readily attached to and removed from a tubular structure orframe. In particular, the present invention is directed to a portablelight source that is compact, versatile and rugged enough to function asa safety headlamp for a bicycle, and which can be upgraded for use in avariety of different riding situations.

BACKGROUND OF THE INVENTION

Most headlamps that are used on bicycles are intended to be attached tothe tubular handlebar of the bicycle. In a conventional bicycle, thehandlebar includes a crosspiece that is oriented in a directionperpendicular to the frame of the bicycle. Typically, a bicycle headlampis designed to be attached to this crosspiece so that it projects a beamof light in the forward direction of the bicycle.

Recently, aerodynamically styled handlebars have become popular. Quiteoften, these types of handlebars do not have a crosspiece which isperpendicular to the direction of movement of the bicycle. Rather, allof the various sections of the handlebar are contoured to fit therider's profile, and do not offer a suitable location for mounting aheadlamp that is designed to be attached to a perpendicular crosspiece.As a result, if a headlamp of this type is mounted to the handlebar, itsbeam points in a direction other than the forward direction of thebicycle.

There are some headlamps available that include a swivel mount to allowthe lamp to be rotated so that it always points in the forward directionof the bicycle, regardless of the orientation of the mounting clampitself. These types of headlamps are typically attached to the bicyclehandlebar with the use of screws, or other mechanisms which requiretools. As a result, it is not convenient for the bicycle rider to easilyattach and remove the headlamp from the handlebar. For example, if it isnecessary to perform repairs upon the chain or rear tire of the bicycleduring nighttime riding, it is desirable for the rider to be able toremove the headlamp from the handlebar and place it near the rear of thebicycle while the repairs are being carried out. When the removal andremounting requires tools, however, the rider is not inclined to carryout this action in addition to the necessary repairs.

To facilitate removal, some bicycle headlamps are comprised of twoseparable assemblies, a mounting assembly and the headlamp itself. Thesesystems enable the headlamp to be removed and located at a convenientposition for effecting repairs. However, the mounting assembly still isattached to the handlebar by means of screws or the like, so that it isnot readily removable from the bicycle without tools. It is not uncommonfor a bicycle rider to own two or more different bicycles, for example,for different riding conditions. If the rider desires to be able toreadily mount the headlamp on either of the two bicycles, it isnecessary to obtain a second mounting assembly, so that each bicycle hasits own, permanently attached mounting assembly. This type of system isnot totally acceptable, because of the cost associated with a secondmounting assembly and the unsightliness of having a mounting assemblyattached to the bicycle when the headlamp is not in use.

Further along these lines, bicycle headlamps are typically designed fora single type of riding situation. For reasons of affordability, themajority of the headlamps provide low power lighting, which is suitablefor most on-road riding situations. These types of headlamps containinternal batteries such as dry cells or rechargeable Ni-Cad cells whichmust be removed from the headlamp for charging. Some riding situations,such as off-road riding, have higher power lighting requirements.Headlamps designed for this purpose may have an external power source,such as a battery pack or a generator driven by the bicycle wheel.Typically, a headlamp designed for low-power requirements cannot beadapted to accommodate a high-power lighting situation. It is desirable,therefore, to provide a single headlamp which can be readily adapted foreither type of lighting requirement.

Another concern that relates to of headlamps for bicycles is thelocation of the center of gravity of the headlamp relative to themounting point. In many headlamp designs, the headlamp is in acantilevered relationship with respect to the handlebar. In these typesof designs, the center of gravity of the headlamp is not aligned withthe handlebar or other mounting point. When the bicycle undergoes animpact, such as the type that is typically encountered in off-roadriding, the force of the impact will cause the cantilevered mountingarrangement to rotate about the axis of the handlebar. Consequently, theheadlamp might be pointing in a downward direction, rather thanforwardly of the bicycle. As a result, the appropriate area will not belighted and the rider will be forced to remove his hand from thehandlebar and realign the position of the headlamp, posing aninconvenience and a safety hazard.

BRIEF STATEMENT OF THE INVENTION

The present invention provides a compact, rugged and versatile lightingsystem that is particularly suitable for use with bicycles andencompasses all of the features desired by the discriminating rider. Onefeature of a headlamp incorporating the present invention is a mountingsystem which requires no tools to install or remove, and which can beeasily attached to any of a number of different areas on a bicycle. Theflexible mounting system includes a clasp and strap arrangement whichcan be clamped on any tubular area of the bicycle, such as a handlebar.A flexible strap wraps around the attachment position, and the clasptensions the strap and locks the headlamp in position. The clasp isattached to a main mounting seat by means of rotary nibs that form arotational axis for the clamp. The point of attachment of the strap tothe clasp is offset from the nib axis so that, as the clasp is rotatedabout the nib axis, the strap is tensioned in a manner which holds theclasp in its fixed position. Because of the ease of use afforded by thisarrangement, the headlamp can be easily fixed at any position on abicycle to direct a beam of light in a desired direction, and can bereadily moved from one bicycle to another without requiring extra parts.

Another feature of the headlamp according to the present invention is ahousing which contains all of the components of the headlamp, includingthe batteries, in a compact, economical and rugged manner. The housingis designed such that the center of gravity of the headlamp coincideswith the gravitational forces acting on the headlamp, so no moment armsare created that would cause the headlamp to rotate about its mountingpoint when the bicycle is subjected to impact.

A further feature of the mounting system is a rotational arrangementthat enables the housing to be rotated to any position relative to themounting point, to provide flexibility for the location of the headlampon the bicycle. The rotational arrangement includes a main screw that islocated along the rotational axis and connects the various components ofthe headlamp together. A clamp coupling isolates the screw from therotational movement, to thereby prevent loosening of the screw when thelamp is rotated. In addition, the clamp coupling and screw arrangementallows the degree of friction between the housing and the mountingassembly to be adjusted to a level suitable to the user. The combinationof the flexible mounting system and the rotary joint allow the beam oflight to be pointed in any direction without concern over theorientation of the structure on which it is mounted.

A further feature of the headlamp according to the present invention isan adjustable focusing mechanism that allows the operator to vary thelight distribution pattern. The focusing mechanism is designed to allowthe operator to adjust the distribution pattern through rotation of alens reflector assembly, relative to the housing. Due to its design, thelens reflector assembly can be rotated an unlimited number of times ineither direction to adjust focus, without loosening or binding theassembly. Thus, in combination with the quick release mounting system,the headlamp can be readily switched from a road bike, where a narrowbeam is desirable for high speed riding, to an off-road bike, where awider beam is preferred.

Along these same lines, the lighting system of the headlamp isupgradeable to accommodate the desires of different users and therequirements of different riding situations. In its most economicalform, the headlamp comprises a self-contained, battery-powered systemthat provides low power lighting that is suitable for most ridingconditions. For those riders who desire a greater amount of light, ahigher wattage light bulb can be readily inserted, and high powerrechargeable batteries can be used. For this arrangement, the headlampincludes a jack to enable the batteries to be recharged without the needto remove them. If a greater amount of power and/or longer battery lifeare desired, an external battery pack or generator is connectable to theheadlamp through the same jack.

The combination of all of these features provide, in a single unit, aheadlamp which is sufficiently compact and versatile to meet the needsof a number of different types of bicycling enthusiasts. Furtherfeatures and advantages of the present invention are describedhereinafter with reference to a preferred embodiment illustrated in thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the exterior of a portable headlampconstructed in accordance with the present invention;

FIG. 2 is a perspective view of the headlamp mounted on the handlebar ofa bicycle;

FIG. 3 is a cross-sectional side view of the headlamp;

FIG. 4 is a perspective view of the focus barrel and light bulb,illustrating various positions relative to the reflector;

FIG. 5 is a perspective view of the quick-release mounting mechanism;

FIG. 6 is a cross-sectional side view of the mounting clasp relative tothe mounting seat;

FIG. 7 is a perspective view of the electrical components of theheadlamp;

FIG. 8 is an exploded view of the electrical components of the headlamp;

FIG. 9 is a side view of the positive battery contact plate; and

FIGS. 10 and 11 are perspective views of headlamp arrangements whichinclude an external battery pack, mounted on a bicycle.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

A portable headlamp constructed in accordance with the present inventionis particularly suited for use with bicycles. To facilitate anunderstanding of the features of the headlamp, it is describedhereinafter with particular reference to its use on a bicycle. As willbecome apparent from the following description, however, the applicationof the headlamp is not limited to this particular environment. Rather,the headlamp can be used in any situation in which it is desirable tohave a portable light source that can be readily attached to a tube orpole, and that can be directed to shine a beam of light in any desireddirection without regard to the orientation of the structure on which itis mounted.

A perspective view of a bicycle headlamp in accordance with the presentinvention is shown in FIG. 1. The headlamp comprises a housing 10 thatis generally L-shaped. To facilitate insertion and removal of batteries,the housing is divided into two parts, an upper housing 12 and a lowerhousing 14. Generally speaking, the lower housing 14 defines ahorizontal axis or leg for the body, and the upper housing 12 defines avertical axis or leg of the L-shaped body.

Attached to the upper end of the upper housing 12 is a clamp seat 16.The clamp seat 16 is rotatable relative to the housing 10, and defines amounting surface 18 which abuts the tube or pole to which the headlampis to be attached. Preferably, the surface 18 has a concave contour toaccommodate a tube or pole. A strap (not shown in FIG. 1) is attached tothe clamp seat to be wrapped around the tube or pole, to hold theheadlamp in place. To this end, the clamp seat includes a pair of spacedhorizontal bars 20 and 22 on one side thereof. These bars provide anadjustable attachment for the strap. On the opposite side of the clampseat is located a pair of spaced projections 24 having recesses 26 onthe opposed surfaces thereof. As described in detail hereinafter, theserecesses receive a clasp attached to one end of the strap, to secure theheadlamp in place, as shown in FIG. 2.

A focusing ring 28 is attached to the end of the lower housing 14. Thering 28 has a number of spaced projections 30 around its peripheralsurface, to enable it to be readily grasped and rotated relative to thehousing 14. A lens 32 is removably mounted on the focusing ring 28. Forexample, the lens can be attached to the ring 28 by means of abayonet-type mount. Preferably, the lens includes a series ofprojections 34 to enable the lens to be rotated relative to the ring, sothat it can be readily removed for replacement of a light bulb.

FIG. 3 is a cross sectional side view of the headlamp, illustrating itscomponents in greater detail. Located within the housing is a batterycarriage. The battery carriage is preferably formed of two halves 36 and37 which are mirror images of one another, as best seen in FIG. 8. Theinterface of these two halves lies along a vertical plane located on theoptical axis 38 of the headlamp. In the sectional view of FIG. 3, theinside surface of one of the components 36 of the battery carriage isshown. The batteries 39 are attached to the outside of the batterycarriage in a vertically oriented manner, and are shown in phantom inFIG. 3.

The battery carriage is attached to the lower housing, so that itremains in the position shown when the two halves of the housing areseparated. After the batteries have been inserted in place within thecarriage 36, 37, the upper housing 12 is placed on the lower housing, toencase the battery carriage. A threaded connector such as a screw orbolt 42 is passed through the clamp seat 16 and the upper housing 12,and engages a nut 44 that is trapped between the two halves of thebattery carriage. Tightening of the bolt 42 causes the battery carriage36, 37 to be pulled toward the top of the upper housing, until itengages a rib 45 on the underside of the upper housing. Since the bottomof the battery carriage is secured to the lower housing 14, tighteningof the bolt 42 causes the upper housing 12 to be securely attached tothe lower housing. Preferably, a gasket (not shown) is placed betweenthe two portions of the housing, to form a water-tight seal.

The bolt 42 does not directly contact the clamp seat 16. Rather, a clampcoupling 46 is disposed within a bore 48 in the clamp seat 16. The lowerportion of the bore 48 has a conical surface 50, and the clamp coupling46 has a complementary surface. The clamp coupling 46 is secured to thetop of the upper housing 12 by means of hooks 52 which fit into cutoutsin the top of the upper housing. The mating conical surfaces of theclamp coupling and the bore 50 within the clamp seat provide forrotational movement between the clamp seat and the housing 12. Since theclamp coupling 46 is stationary with respect to the housing, the bolt 42is isolated from the rotational movement of the clamp seat 16, i.e., allof the surfaces which the bolt 42 and nut 44 contact are stationaryrelative to one another. Thus, rotation of the housing 12 relative tothe clamp seat 16 will not cause the bolt 42 to become loosened from thenut 44.

With this arrangement, after the battery carriage 36, 37 engages the rib45 on the upper housing, the bolt 42 can be tightened a suitable amountto provide a preferred degree of friction between the clamp coupling 46and the conical surface 50 of the clamp seat 16. Once the proper amountof friction is provided, the bolt will remain in this position tomaintain the selected degree of friction even when the clamp seat andthe housing 12 are rotated relative to one another.

It can be seen from the illustration of FIG. 3 that the bolt 42 liesalong the rotational axis of the clamp seat, and the batteries 39 aresymmetrically disposed about this axis. In addition, the bottom of thecontoured surface 18 of the clamp seat 16 is located along the verticalrotary axis. Since the batteries constitute the heaviest componentswithin the headlamp, the arrangement illustrated in FIG. 3 causes thecenter of gravity of the headlamp to be located substantially near thevertical rotary axis. When the headlamp is mounted underneath thehandlebar in the position shown in FIG. 2, its center of gravity islocated almost directly below the point of attachment to the handlebar.As such, when a bicycle undergoes sudden impact caused by a bump or thelike, the gravitational forces on the headlamp will cause it to remainin place, rather than create a moment arm which causes it to rotateabout the handlebar on which it is mounted.

The optical axis of the headlamp is coincident with the horizontal axisof the L-shaped body. Located within the horizontal leg of the body is areflector 54. The reflector 54 is mounted on the focussing ring 28, forrotation therewith. For example, the circumferential surface of thereflector 54 can be provided with recesses 56 that mate withcorresponding bosses 58 on the interior of the focussing ring 28, sothat these two components move in unison. The reflector has a suitableparabolic or elliptical shape, to provide a beam of light of desiredwidth. A sleeve 60 is provided in the center of the reflector, toaccommodate a focussing barrel 62 which houses a light bulb (not shownin FIG. 3).

Essentially, the focusing barrel 62 forms a socket in which the lightbulb is mounted. For clarity of the illustration, the light bulb itselfand the electrical connections between the light bulb and the batteriesare not been shown in FIG. 3. The focussing barrel 62 is free totranslate along the optical axis 38, within a channel 64 formed by themating halves of the battery carriage 36. Rotation of the barrel isprevented, however, by means of flanges 66 on the barrel, which ridewithin slots 68 formed along the channel 64.

To impart translational movement to the focussing barrel, and the lightbulb mounted within it, the outer circumferential surface of the barrelis provided with a helical groove or track 70. A pin 71 on the interiorof the reflector sleeve 60 fits within this track. Thus, as thereflector 54 is rotated by movement of the focussing ring 28, thefocussing barrel 62 is caused to translate along the optical axis. As aresult, the position of the light bulb relative to the reflector isvaried, to thereby vary the width of the beam emitted through the lens32.

As best shown in FIG. 4, the track 70 preferably forms a sinusoid aroundthe circumference of the focussing barrel 62. With this type of anarrangement, the focussing ring 28 can be turned in either direction toprovide a narrower or a wider beam. As the ring is turned, the focussingbarrel 62 and the light bulb 72 are translated along the optical axis,as shown by the arrow 73, to vary the width of the beam. The focussingring 28 can be turned in either direction as many times as the userdesires, without reaching a limit and without causing the entirestructure to become unscrewed or otherwise fall apart.

The quick release mounting arrangement for the headlamp is illustratedin greater detail in FIGS. 5 and 6. A strap 75 is attached at one end toone side of the clamp seat 16. To accommodate tubes and poles of varyingdiameter, the strap 75 is preferably attached so that its length can beadjusted. Referring to FIG. 3, a free end of the strap is passed betweenthe body of the clamp seat 16 and the two spaced bars 20 and 22, andthen wrapped around the lower bar 22 and behind the bar 20, to provide asecure connection that is easily adjustable.

The other end of the strap is fixedly attached to a clasp 74. Moreparticularly, the end of the strap is sewn about a bar 76 at the end ofthe clasp. On the exterior of the clasp, at the two opposite sidesthereof, are a pair of aligned nibs 78. These nibs are adapted to fitwithin the recesses 26 on the projections 24 of the clamp seat 16. Thenibs define an axis about which the clasp 74 rotates when the nibs areseated in the recesses 26. As best shown in FIG. 6, this axis is offsetfrom the longitudinal axis of the bar 76 to which the strap is attached.

In mounting the headlamp to a handlebar or the like, the handlebar 79 isaccommodated in the concave mounting surface 18 of the clamp seat 16.The strap 75 is wrapped around the handlebar and the nibs 78 of theclasp 74 are inserted in the recesses 26, with the clasp in the positionshown in phantom in FIG. 6. In this position, the bar 76 lies to oneside of a center line 80 defined by the surface of the handlebar 79 andthe rotational axis of the nibs 78. Thereafter, the clasp 74 is rotatedabout the axis defined by the nib 78, in a clockwise direction as viewedin FIG. 6. As this rotation occurs, the attachment bar 76 approaches thecenter line 80, moving away from the handlebar 79. This movement of thebar 76 causes the strap to be tensioned, thereby securing the mounting.Once the bar 76 crosses the center line 80 of the nib axis, the force ofthe tensioned strap pulls on the bar 76, to maintain the clasp 74securely in place against the handlebar, as illustrated in FIG. 2.Removal of the headlamp from the handlebar, or loosening of theconnection to rotate the headlamp around the handlebar, is easilyaccomplished by merely rotating the clasp 74 from the solid lineposition shown in FIG. 6 to the position shown in phantom.

The components which comprise the electrical system of the headlamp willnow be described with particular reference to FIGS. 7 and 8. As notedpreviously, the light bulb 72 is housed within the focussing barrel 62.The bulb 72 is securely held in place by means of a coiled spring 82mounted within the focussing barrel 62. The coils of the spring functionas threads which enable the bulb 72 to be screwed into the focussingbarrel 62. In addition, the spring provides as an electrical contact tothe casing of the light bulb which serves as a negative terminal. Oneend of the spring is connected to a negative battery contact 84 by meansof a wire 86. The negative battery contact 84 includes a pair of springleaves 88 which engage the negative terminals of a pair of batteriesmounted in the left half 37 of the battery carriage (as viewed in FIG.8).

Interposed between the negative battery contact 84 and the wire 86 is anon/off switch 85. The switch has a button 87 at the bottom thereof,which is accessible through an aperture 89 in the bottom of the lowerhousing 14 (see FIG. 3).

A positive battery contact 90 includes a pair of leaves 92 for engagingthe positive terminals of two batteries mounted in the right half 36 ofthe battery carriage. The contact has a contact blade 94 for makingelectrical contact with the positive terminal 96 on the end of the lightbulb 72. As best illustrated in FIG. 9, the blade 94 has an S-shapedconfiguration. This configuration enables the tip of the blade to remainin contact with the positive terminal 96 of the light bulb 72 as thelight bulb is moved in the directions of the arrow 73 when the focussingting 28 is rotated.

Referring again to FIGS. 7 and 8, a battery contact plate 98 is mountedat the top of the two halves of the battery carriage. The batterycontact plate 98 has four leaves 100 which respectively contact theupper terminals of batteries mounted in the battery carriage, therebyconnecting the positive terminals of batteries mounted in the leftcarriage half 37 to the negative terminals of the batteries mounted inthe right carriage half 36. In addition, the battery contact plate 98functions to hold the two halves 36 and 37 of the battery carriagetogether.

The headlamp is adapted to be readily upgraded to provide the level oflight desired by the user. In its most economical configuration designedfor regular bicycle riding, the headlamp can be provided with a two-wattlight bulb 72, and be powered by four alkaline batteries.

If desired, the headlamp can be upgraded to a rechargeable system, byreplacing the alkaline batteries with rechargeable Ni-Cad batteries. Forthis configuration, the headlamp is provided with a jack that enablesthe batteries to be recharged while they remain mounted within thebattery carriage. The jack includes a circular pin 102 that extends fromthe rear of the positive battery contact 90. The pin 102 is adapted tofit within the axial bore of a female connector plug 104 from a batteryrecharger, as shown in FIGS. 7 and 9. The negative battery contact 84includes a rearwardly extending, spring loaded blade 106 that contactsthe exterior, cylindrical terminal of the connector plug 104. Access tothe jack formed by the pin 102 and the blade 106 is provided by means ofan aperture 108 in the back of the lower housing 14 (see FIG. 3). Foroptimum light output with the rechargeable batteries, the light bulb 72is preferably a halogen bulb.

For greater light output requirements, the two-watt light bulb can beremoved and replaced with a six-watt or ten-watt light bulb. Theexchange of the light bulbs is easily accomplished by means of thebayonet mount for the lens 32, which provides ready access to the lightbulb through the front of the headlamp. To accommodate the greater powerrequirements of the higher wattage light bulbs, the batteries can beremoved from the battery carriage, and an external battery pack orwheel-driven generator can be connected to the light bulb by means ofthe jack formed by the pin 102 and blade 106.

One example of an external battery pack 110 is illustrated in FIGS. 10and 11. The battery pack 110 has a flap which can be wrapped around thehorizontal crossbar 112 of a bicycle frame to secure the pack thereto. Astrap 114 attached to the lower portion of the pack is wrapped aroundthe diagonal frame member 115, to provide stability. The battery pack110 is connected to the headlamp by means of a coiled cord 116.

To accommodate the heat generated by higher wattage light bulbs, atleast the lens 32 and the focussing barrel 62 should be made from ahigh-temperature plastic. If the reflector 54 is not made of metal, itshould also be formed of a high-temperature plastic.

For the greatest amount of light, a dual headlamp system can beemployed, as shown in FIG. 11. One of the headlamps can be provided witha six-watt low beam light bulb, and the other headlamp can contain aten-watt high beam light bulb. Each of the headlamps is connected to theexternal battery pack, and can be selectively turned on and off throughthe switch located at the bottom of the housing. Furthermore, each canbe adjusted to provide a beam of desired width by means of its focussingring.

From the foregoing, it can be appreciated that the present inventionprovides a headlamp having a number of features that contribute to itssuitability for use on bicycles and other environments. The easilyremovable and universally mountable fastening system enables theheadlamp to be mounted at any desired position on a bicycle withoutrequiring tools for the installation. In addition, the rotary jointbetween the mounting arrangement and the main housing of the headlampallows the beam of light to be pointed in any direction without regardto the orientation of the particular structure on which the headlamp ismounted. Further, the combination of the quick release mountingmechanism, the adjustable focus of the light beam and the upgradeabilityof the electrical system allows the headlamp to be readily used ondifferent bicycles for different types of riding conditions, withoutrequiring additional hardware for each bicycle.

It will be appreciated by those of ordinary skill in the art that thepresent invention can be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresently disclosed embodiments are considered in all respects to beillustrative and not restrictive. The scope of the invention isindicated by the appended claims rather than the foregoing description,and ail changes that come within the meaning and range of equivalencethereof are intended to be embraced therein.

What is claimed is:
 1. A bicycle headlamp, comprising:a generallyL-shaped housing having a lens located at an end of one of the legs ofthe housing for projecting a beam of light along an optical axis that isoriented along said leg of the housing; a releasable mounting mechanismattached to an end of the other leg of said housing for enabling theheadlamp to be readily mounted upon and removed from a tubular member ofa bicycle; a rotary joint disposed between said housing and saidmounting mechanism for providing rotational movement of said housing,relative to a member of the bicycle upon which the mounting mechanism ismounted, about an axis along said other leg of the housing; and abattery compartment disposed within said other leg of said housing sothat the center of gravity of said headlamp, when loaded with batteries,lies substantially along said rotational axis.
 2. The bicycle headlampof claim 1 further including a light source mounted within said one legof the housing, a reflector disposed within said housing in operativerelationship with said light source and said lens to reflect light fromthe light source through said lens, and means for moving said lightsource along said optical axis, relative to said lens and saidreflector, to vary the angle of a beam of light emitted through saidlens.
 3. The bicycle headlamp of claim 2 wherein said moving meansincludes a tubular sleeve which forms a socket into which said lightsource is mounted, said sleeve having a helical track disposed on theouter circumferential surface thereof, a projection on said reflectorwhich rides along said track, and means for enabling said reflector tobe rotated about said optical axis, so that rotation of said reflectorabout said optical axis imparts translational movement of said sleeveand light source along said optical axis.
 4. The bicycle headlamp ofclaim 3 wherein said track comprises a double helix that forms asinusoid, so that continued rotation of said reflector in one directionimparts bidirectional movement of said sleeve and light source alongsaid optical axis.
 5. The bicycle headlamp of claim 1, wherein saidmounting mechanism at said end of said other leg enables said headlampto be suspended below the tubular member of a bicycle with said axis ofsaid other leg of the housing being oriented in a generally verticaldirection such that said center of gravity lies below the tubularmember, and said one leg of said housing is oriented in a generallyhorizontal direction.